Carrier Aggregation (CA) is a technique to increase bandwidth, and hence bitrate, of the air interface between a wireless communication network and a subscriber's User Equipment (UE). In CA, two or more component carriers (CC) are modulated with data, and the UE receives (or transmits) data from (or onto) all specified CCs. This both increases peak user data rates and overall network capacity, and allows operators to exploit fragmented spectrum allocations.
Release 10 of the 3GPP Long Term Evolution (LTE) standard introduced a limited form of CA, called Dual Cell (DC), which allowed the aggregation of two intra-band contiguous CCs (FDD or TDD) or two inter-band non-contiguous CCs (FDD only). CA was expanded in Rel. 11 to allow aggregation of two intra-band non-contiguous CCs (FDD or TDD). Rel. 12 expanded the number of CCs that may be aggregated, introduced CA in the uplink, and provided a framework for aggregation between FDD and TDD carriers. Rel. 13 further expanded the number and types of aggregated CCs, and allows aggregation between licensed and unlicensed spectrum. As of Rel. 13, aggregation of up to eight contiguous CCs is defined. Each CC may have a bandwidth of 1.4, 3, 5, 10, 15, or 20 MHz. Hence, the maximum defined bandwidth is 8×20 MHz=160 MHz.
To effectively configure each UE for CA, the network must be aware of the UE's capabilities. UEs communicate these capabilities to the network when in the RCC connected state; the network transfers this information to a target serving node during handover. The serving node need not maintain each UE's CA capabilities in RCC idle state. To avoid re-transmitting this information upon every transition to connected state, the serving node may upload the CA capability information to a Mobility Management Entity (MME), and retrieve when a specific context for the UE is created, as the UE transitions to RRC connected state.
The CA capability uplink signaling defined through Rel. 13 (referred to herein as legacy signaling) is centered on the aggregated bands. For each supported band combination, the UE reports its capability with respect to RF features, such as the supported frequency bands and band combinations, carrier bandwidths, whether it supports multiple TimingAdvance or simultaneous Tx/Rx, number of MIMO antennas, and the like. Additionally, for each band the UE reports baseband (BB) capabilities, such as the number of MIMO layers it can process, the number of Channel State Information (CSI) processes supported, Network Assisted Interference Cancellation (NAIC) capability in CA, and the like. Since this information is separately reported for each supported band combination, as CA capabilities expand and UEs are capable of supporting many combinations of CCs, the data reported to the network becomes voluminous, and much of it is repeated. Furthermore, legacy signaling requires the UE to report separately its fallback capabilities—that is, if one or more CCs becomes unavailable, which lower-order CA the UE supports (and all of its capabilities for each fallback combination). Future 3GPP Releases are expected to support up to 32 aggregated carriers (in uplink as well as downlink). For large numbers of aggregated carriers, legacy CA signaling will impose too great a burden on system overhead. Indeed, transmission of CA capability per UE will likely exceed the current PDCP PDU size limit, for transmission over the air interface, of 8080 bytes.
As used herein, the non-limiting term radio network node or simply network node refers to any type of node of a wireless communication network that is serving UE and/or connected to other network node or network element or any radio node from where UE receives signal. Examples of radio network nodes are Node B, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNode B, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), and the like.
As used herein, the non-limiting term user equipment (UE) refers to any type of wireless device communicating with a radio network node in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, machine type UE or UE capable of machine to machine (M2M) communication, PDA, iPAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, and the like.
Embodiments of the present invention are described herein with respect to the 3GPP EUTRA/LTE system. The embodiments are however applicable to any RAT or multi-RAT system where the UE operates with UL feedbacks consisting of channel status estimated from UE side e.g. UTRA/HSPA, GSM/GERAN, Wi Fi, WLAN, WiMax, CDMA2000, and the like.
As used herein, the term carrier aggregation (CA) is synonymous with the terms “multi-carrier system”, “multi-cell operation”, “multi-carrier operation”, “multi-carrier” transmission and/or reception.
Embodiments of the present invention are applicable to a UE capable of at least one receive antenna and also apply to UE with two or more receive antennas. The embodiments are also applicable in conjunction with MIMO in which the UE is able to receive and/or transmit data to more than one serving cells using MIMO, e.g., 2, 4 or 8 receiver antennas at the UE.
Each UE is served by at least one serving cell (also known as a first serving cell or simply a primary serving cell), which in turn is managed or served by a first network node. The UE may also be served by plurality of serving cells, e.g., a first serving cell such as a Primary Cell (PCell), a second serving cell such as a first Secondary Cell (SCell), a third serving cell such as a second SCell, and so on in CA. In dual connectivity a first serving cell may be PCell and a second serving cell may be a PSCell and third and additional serving cells may be SCells. Different serving cells may be managed or served by the same first network node or by different network nodes, e.g., PCell by the first network node and SCell(s) by a second network node and so on.
The UE reception of signals from the serving cell may also be interfered by signals from one or more interfering cells, also known as inter-cell interference. For example, UE reception from the first serving cell may be interfered by a first interfering cell.
As used herein, the term time resource refers to a temporal division or duration defined by the applicable standard. Examples of time resource include time slot, transmission time interval (TTI), subframe, symbol, frame, scheduling period, data and/or control channel reception time or instant, and the like. Typically, the UE can be scheduled during each time resource (e.g., subframe) and therefore the UE generally monitors one or more control channels during each time resource for determining whether the UE is scheduled or not.
The UE is scheduled with the data in downlink (i.e., receives data) on one or more data channels but at least a first data channel (e.g., PDSCH) from at least the first cell. Therefore data reception corresponds to DL PDSCH demodulation in LTE system.
In some embodiments, data structures such as lists or information elements are described using particular notations. These notations are only provided as examples; those of skill in the art will recognize that other notation may be used.